The Myth of Cutting a Worm In Half

“Is it true if you cut a worm in half that both parts will regenerate and you will have 2 worms?” ~ Steve

Hi Steve – before you go grab the scissors and try to double your worm population (haha), let me assure you that this is in fact a myth.

What you will end up with if you cut an earthworm in half is either a dead worm, or a shorter worm and half a worm carcass (which will decompose quite quickly).

The anterior (head) region is the most important part of a worm – if it remains intact the worm can potentially survive, and may even grow a new tail (often somewhat stubby in appearance). The lower fragment however, once cut off from the rest of the worm, will simply die.

There ARE in fact types of “worm” that can indeed regenerate from body fragments.

Certain types of flat worms, such as planarians, are an example of a worm-like organism that can split in half to produce two new worms – in fact this is a form of asexual reproduction planarians can use to increase population size.

These ‘worms’ are not related in any way to the earthworms however – while they are both in the kingdom Animalia, they are in entirely different phyla – flat worms are part of the phylum Platyhelminthes, while the true worms belong to phylum Annelida.